Browsing by Subject "IPSC GENERATION"
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(2015)Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSC) by the forced expression of the transcription factors OCT4, SOX2, KLF4 and c-MYC. Pluripotent reprogramming appears as a slow and inefficient process because of genetic and epigenetic barriers of somatic cells. In this report, we have extended previous observations concerning donor age and passage number of human fibroblasts as critical determinants of the efficiency of iPSC induction. Human fibroblasts from 11 different donors of variable age were reprogrammed by ectopic expression of reprogramming factors. Although all fibroblasts gave rise to iPSC colonies, the reprogramming efficiency correlated negatively and declined rapidly with increasing donor age. In addition, the late passage fibroblasts gave less reprogrammed colonies than the early passage cell counterparts, a finding associated with the cellular senescence-induced upregulation of p21. Knockdown of p21 restored iPSC generation even in long-term passaged fibroblasts of an old donor, highlighting the central role of the p53/p21 pathway in cellular senescence induced by both donor age and culture time. (C) 2015 The Authors. Published by Elsevier B.V.
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(2022)Conventional reprogramming methods rely on the ectopic expression of transcription factors to reprogram somatic cells into induced pluripotent stem cells (iPSCs). The forced expression of transcription factors may lead to off-target gene activation and heterogeneous reprogramming, resulting in the emergence of alternative cell types and aberrant iPSCs. Activation of endogenous pluripotency factors by CRISPR activation (CRISPRa) can reduce this heterogeneity. Here, we describe a high-efficiency reprogramming of human somatic cells into iPSCs using optimized CRISPRa. Efficient reprogramming was dependent on the additional targeting of the embryo genome activation-enriched Alu-motif and the miR-302/367 locus. Single-cell transcriptome analysis revealed that the optimized CRISPRa reprogrammed cells more directly and specifically into the pluripotent state when compared to the conventional reprogramming method. These findings support the use of CRISPRa for high-quality pluripotent reprogramming of human cells.
